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H. 0. LUTHER.

UNDERCUT IMITATION sToNE- Patented Dec. 18, 1883.

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UNITED STATES PATENT OFFICE HENRY G. LUTHER, OF PROVIDENCE, RHODE ISLAND.

UNDERGUT IMITATION STONE.

SPECIFICATION forming part of Letters Patent No. 290,442, dated December 18, 1883. Application filed -Mav 25, 1881. Renewed February 2, 1883. (No model.)

To all whom it may concern:

Be it known that I, HENRY O. LUTHER, of Providence, in the State of Rhode Island, have invented an Improvement in Undercut Imitation Stone, of which the following is a specification.

The nature of my invention consists in forming the under-cut in imitation stone in the body of the stone, instead of upon a projecting boss or shank, as heretofore.

Figure 1 represents a plan view of the back side of a circular imitation stone undercut according to my improvement. Fig. 2 repre sents a section of the same, taken in the line 00 w of Fig. 1, also showing a section of the at tached metallic piece. Fig. 3 represents an elevation of the metallic piece previous to attach ment. Fig. 4 represents a central section of Figs. 5 and 6, taken in the lines x m. Fig. 5 represents a plan view of the back side of a square undercut imitation stone. Fig. 6 represents a plan view of the back of an elongated rectangular undercutstone. Fig. 7 represents the undercut imitation stone as commonly formed.

In the drawings, A represents an imitation stone provided with an undercut central portion, a, the under-cut being made in the body of the stone and toward its center or axis. The inclined groove 1), which forms theundercut, may be continuous. as shown in Figs. 1 and 5, or two grooves, b b, may be made opposite each other, as shown in Fig. 6. The rim 0 of the metallic piece B is turned inward around the undercut central portion, a, thus securely fastening the metallic and non-me tallic parts together. In the case of Figs. 5

and 6 the fastening may be formed by simply bending the edges of a plain plate downward and inward, so as to clasp the central undercut portion, a.

What is known as undercut imitation stone has hitherto been made as shown in Fig. 7', where the under-cut is made on a boss or shank projecting from the face of the back; but in this form the fastening has been made too prominent, and the back of the'stone could not bebrought down as close as required. Imitation undercut stone is formed in a plastic condition, and the form shown in Fig.7 has heretofore been considered the only form in which the proper undercuttingdies could be made to work practically, the jaws of the dies being made to move back and forth in a plane parallel with the plane of the back of the stone. In my improvement I cause the dies to move back and forth in planes at an angle with each other, and converging toward the body and central portions of the plastic material. I am thus enabled to form an undercut imitation stone where the attaching-clasp of the metallic portion is properly disposed of and concealed by the outer edges of the stone.

I claim as my invention A pressed imitation stone provided on its back with a molded groove inclining inward, so as to undercut the central portion, and also to sink below the plane of the surface of the adjoining exterior portion of the back of the stone, substantially as and for the purpose specified.

HENRY O. LUTHER.

WVitnesses:

S. ScHoLEIELn, WV. H. JoYoE. 

